Secondary recovery process



July 9, 1957 Filed June 8, 1953 G. G. BINDER, JR., ETAL 2-;798556 SECONDARY RECOVERY PROCESS 2 Sheets-Sheet l GEORGE G.BINDER, JR. LOREN H. JENKS INVENTORS July 9, 1957 Filed June 8, 1953 WELL G. G. BINDER, JR, ET AL SECONDARY RECOVERY PROCESS 2 Sheets-Sheet 2 WELL FIG.2

at a practical and economic rate.

TPatented July 9, 1957 2,798,556 SECONDARY RECOVERY PROCESS George G. Binder, Jr., and Loren H. Jenks, Tulsa, Okla, assignors to Esso Research and Engineering Company, a corporationof Delaware Application June 8, 1953 Serial No. 360,184

8 Claims. (Cl.'166--9) The present invention is broadly concerned with an improved process for the increased .recovery of crude petroleum from oil-bearing formations. The invention is particularly concerned with an improved method for the utilization of liquefiable solvents, which may be normally gaseous hydrocarbons, .for the more complete recovery of oil from subterranean reservoirs. In accordance with the present invention, a quantity of liquid normally gaseous hydrocarbons, which are substantially completely miscible with the crude oil, .is caused to pass through a selective reservoir in relatively narrow, long paths. The .solventmay be directed along the selccted path in accordance with the present invention either by a gas or Water drive. After the oil is recovered from an initial predetermined narrow path, this initial path is water-flooded so as to further contain the oil being recovered in adjacent selected paths.

In conventional crude oil-producing operations, situaliens are frequently encountered wherein oil wells cease to produce at practical rates even though it is known with certaintythat all available, recoverable oil has not been obtained from the field. This diminution in oil production from a given wellv'may be the result of a number of factors. Generally speaking, in fields not subject to an active -water drive, the pressure remaining in the particular oil-producing strata may not be sufficient to cause oil to flow toward and into the well bore Thus, the wellsof a field tend to become exhausted with respect to primary methods, even when it is known that relativelylarge quantities of oil are still retainedin the reservoirs.

In oil fields characterized by a significant degree of structural relief, it is common practice to extend the active life of the field by maintaining its pressure artificially as by injecting gas into the gas cap of the reservoir or by injecting Water into the porous formation at a level below that of the producing wells. In addition, it is commonlyknown tolincrease the life of a field beyond the normal limit by secondary recovery methods such as by water flooding, in which water .is continuously injected into the producing sand through injection wells and displaces a portion of the residual oil forward into production wells. .A similar typeof operation may be carried out with gas recycled at low pressure and production increased by this gas drive technique. In both of these latterprocedures, the motion of the oil forward to producing wells after an initial displacement phase results from the frictional' drive of the injected fluids on the residual oil as the injected fluids move from the injection to the producing wells. As a result of these relatively ineffective methods of removing oil from the porous sand, substantial quantities of oil remain behind, even after such secondary recovery operations have in turn reached their economic limits.

The gas and water drives heretofore discussed have generally employed relatively low pressures. More recent proposals for secondary recovery of oil from reservoirs have included the suggestion that gas be recycled at extremely high pressures. Under these conditions, improved recovery of residual oil is obtained because of the increased volume and decreased viscosity of the oil in the reservoir due to solution of components of the gas in the reservoir oil, and due to the increased tendency for vaporization of oil in the high pressure gas. The latter phenomenon is an attribute of operation in the retrograde condensation range in the neighborhood of the critical phase conditionsof the reservoir hydrocarbon mixture.

Another procedure is to fill the entire oil reservoir, preferably at increased pressure, with a light hydrocarbon or hydrocarbon mixture or otherrelatively low viscosity substance soluble in the oil and then to flush out the reservoir with water. In general, it 'is felt that by this method the injected solute -is caused to dissolve in the oil which lessens its viscosity and increases its volume and greatly increases its flowability through the formation. As an alternate to using a single hydrocarbon such as propane alone, the use of natural gas containing light hydrocarbons such as ethane, propane or butane has also been proposed for'this purpose. In generahthemethods of this type heretofore proposed cause the low boiling hydrocarbon or equivalent material to dissolve in the oil, thereby reducing its viscosity, increasing its volume and .thus permitting increased recovery of the oil by subsequent water flooding.

In the present invention, it is proposed to use propane or other readily liquefiable low-boiling hydrocarbon or such other .liquefiahle substance as possess a substantial degree of miscibility with crude oil such as liquefied carbon dioxide. The operation is *carriedout in a manner that oil is produced progressively from parallel relatively long narrow selected sections of the field. 'As :each section is depleted, it is filled with water to prevent overflow of gas and solvent from selected adjacent sections. The process of the present inventionmay be more fully understood by reference tothe drawings illustrating embodiments of the same.

Figure 1 illustrates an operation wherein 'the solvent is passed progressively throughadjacent strips.

Figure 2 illustrates an operation wherewater injection is utilized so asto positively contain the selective paths.

Referring specifically to Figure l, a typical field pattern is illustrated with, for instance, IO-acre spacing with the wells designated by circles and enumerated by the Figures 1 to 25 respectively. In accordance with one adaptation of the present invention, a liquid pool or bank of normally gaseous hydrocarbons '.is introduced into well 5 with wells 6 to 25, inclusive, cut off or sealed. This liquid pool .of normally gaseous hydrocarbons as, for example, liquid propane, is causedto flowin the direction of Well 1. The driving force may either be a gas drive as, for example, natural gas, or may comprise a Water drive, which is injected after the injection of the liquid propane.

Under these conditions, crude petroleum will be produced from wells 1 to 4, inclusive. When the bank of liquid propane reaches Well A it will tend to be produced from this well. At thispoint, well 4 is cut cit until the bank of liquidpropane passes well 4.

After thebank of liquid propane has passed well 4 it is desirable "to injectthe drivingfiuid intowell 4 and thus force the liquid bank further along toward well 1. Under these conditions crude petroleum will be produced from wells 1 to 3, inclusive. When the bank of liquid solvent reaches well 3, well 3 is cut off until the liquid pool moves past well 3. After the liquid pool or mass of liquid solvent has passed by well 3 it is preferred to cut out wells 4 and 5, and to inject the driving fluid as, for example, gas or water, into well 3 and thus further drive the liquid solvent in the direction of well 1.

In a similar manner, well 2 is cut out when the pool reaches well 2 until the mass of solvent passes by well 2. At this point, well 3 is also cut out and the driving fluid preferably is injected through well 2, thus causing the pool of solvent to flow in the direction of well 1.

Under the conditions as described, the path of flow will tend to spread as the mass of liquid flows from well 5 to well 1. This lateral widening of the path of flow is illustrated by line 26.

If a gas drive has been utilized for motivating the flow of liquid solvents, it is desirable in accordance with the present process to flood the area illustrated by line 26 by the injection of water into wells 1 to 5, inclusive after the liquid solvent has passed these wells. However, if a water drive has been employed the area will be flooded without the additional water-flooding operation.

In accordance with the present process, the area illustrated by line 27 is then processed in a manner similar to that described with respect to area 26. This is secured by the injection of the liquid solvent into well 10, and by driving the liquid solvent in the direction of well 6 by the technique described with respect to area 26.

In a similar manner areas 28, 29 and 30 are processed by the described technique. In moving the liquid solvent from one path to another it is preferred to recover the liquid solvent from well 1 and to reinject it into Well 10. Thus, for example, it is desired to remove the solvent from the reservoir from well 16 and to reinject it into well 25. It is to be noted that a preferred mode of operation is to move the liquid solvent in one direction of a predetermined selected path and to move the solvent in the other direction of an adjacent path.

Referring specifically to Figure 2, another typical field pattern is illustrated with the wells numbered 31 to 55, inclusive. In accordance with this adaptation of the present invention, water is injected into wells 31 to 35, inclusive, wells 41 to 45, inclusive, and into wells 51 to 55, inclusive. By this mode of operation oil will be ejected from areas 56, 58 and 60 into areas 57 and 59. The areas 56, 58 and 60 will be water flooded, thus setting up relatively restricted areas 57 and 59. These relatively long paths 57 and 59 will have a relatively high concentration of crude oil due to the fact that oil from areas 56, 58 and 60 has been forced into areas 57 and 59. In accordance with this modification of this invention, a liquid solvent is caused to flow through areas 57 and 59 in accordance with the technique described with respect to Figure 1.

The present invention is broadly concerned with a novel procedure for the more efficient recovery of crude petroleum oil from reservoirs after primary recovery methods have been exhausted. In accordance with the present process, a band of relatively volatile liquid, miscible with oil, as for example propane or butane, is caused to flow through a selected narrow path of the oil-bearing formation. This band of liquid is caused to flow by utilizing either a gas or water drive. By operating as described, efficient recovery of the oil is secured through the use of a limited amount of propane or an equivalent solvent. Furthermore, eflicient recovery of residual propane from the formation is readily secured.

What is claimed is:

1. Process for the recovery of oil from a subterranean reservoir penetrated by a plurality of wells arranged in a plurality of essentially parallel rows whch comprises injecting a bank of liquid solvent miscible with crude oil into a first well at one end of a selected row, driving said solvent bank towards a second well at the opposite end of said selected row by injecting a fluid driving agent into said first well behind said solvent bank, removing produced oil from said second well, continuing the drive of solvent toward said second well until said bank reaches said second well, flooding the flow path between said first and second wells with water, closing off said first and second wells, and thereafter repeating the said steps of solvent bank injection, fluid driving agent injection and oil removal in an adjacent row of wells, utilizing a well at one end of said second row as the injection well and a well at the opposite end of said second row as a producing well, whereby to obtain an efiicient recovery of oil from said reservoir with limited quantities of said solvent.

2. Process as defined by claim 1 wherein said solvent comprises liquefied propane.

3. Process as defined by claim 1 wherein said driving agent comprises a gas.

4. Process as defined by claim 1 wherein said driving agent comprises water, whereby said flooding step is accomplished simultaneously with said step of driving said solvent bank toward said second well.

5. Process as defined by claim 1 wherein said second row of wells is immediately adjacent said first row and wherein the injection well of said second row is immediately adjacent the said second well of said first row whereby the liquid solvent will be driven in said second row in a path directly opposite the path of travel in said first row.

6. Process as defined by claim 1 including the steps of initially producing oil from each well intermediate said first well and said second well, cutting off production from a particular well as the solvent bank reaches that well and then injecting said fluid drive agent into that well after said solvent bank has passed that particular well.

7. Process as defined by claim 1 including the initial step of injecting water into all of the wells in selected alternate rows of wells, thereafter driving said solvent bank through the paths constituting the intermediate rows of wells, in the manner defined.

8. A process for the recovery of oil from a subterranean reservoir that is penetrated by a plurality of wells arranged in a plurality of essentially parallel rows which comprises in combination the steps of injecting a bank of liquid solvent miscible with crude oil into a first well in a selected row; driving said solvent bank toward a second well in said selected row which is spaced from the first well by injecting a fluid driving agent into said first well behind the solvent bank; removing produced oil from said second well; continuing the drive of solvent toward said second well and withdrawing the bank from said second well; flooding the solvent bank flow path between said first and second wells with water; closing off said first and second wells; thereafter repeating said combination of steps sequentially in the remaining rows of the reservoir to move the solvent bank progressively through the reservoir, a row immediately adjacent said selected row being the next row in the sequence.

References Cited in the file of this patent UNITED STATES PATENTS 1,826,371 Spindler Oct. 6, 1931 1,872,906 Doherty Aug. 23, 1932 2,669,306 Teter et al. Feb. 16, 1954 2,718,263 Heilman et al. Sept. 20, 1955 

8. A PROCESS FOR THE RECOVERY OF OIL FROM A SUBTERRANEAN RESERVOIR THAT IS PENETRATED BY A PLURALITY OF WELLS ARRANGED IN A PLURALITY OF ESSENTIALLY PARALLEL ROWS WHICH COMPRISES IN COMBINATION THE STEPS OF INJECTING A BANK OF LIQUID SOLVENT MISCIBLE WITH CRUDE OIL INTO A FIRST WELL IN A SELECTED ROW; DRIVING SAID SOLVENT BANK TOWARD A SECOND WELL IN SAID SELECTED ROW WHICH IS SPACED FROM THE FIRST WELL BY INJECTING A FLUID DRIVING AGENT INTO SAID FIRST WELL BEHIND THE SOLVENT BANK; REMOVING PRODUCED OIL FROM SAID SECOND WELL; CONTINUING THE DRIVE OF SOLVENT TOWARD SAID SECOND WELL AND WITHDRAWING THE BANK FROM SAID SECOND WELL; FLOODING THE SOLVENT BANK FLOW PATH BETWEEN FIRST AND SECOND WELLS; THEREAFTER REPEATING SAID COMBINATION OF STEPS SEQUENTIALLY IN THE REMAINING ROWS OF THE RESERVOIR TO MOVE THE SOLVENT BANK PROGRESSIVELY THROUGH THE RESEVOIR, A ROW IMMEDIATELY ADJACENT SAID SELECTED ROW BEING THE NEXT ROW IN THE SEQUENCE. 